Revert "Revert "add new jira hook for REST-API and adapt README to match new hook""

This reverts commit 30bd3b0878f8d955d7af3256b4ed06b7271d66d9.

Conflicts:

	README.md
insert git-jira-hook for REST-API again
Revert "Revert "add GPL License file""

This reverts commit 20aef2be8b06ddfc6797f92534e9dce52b7ba57a.
remove executable flag of README